Maternal antibodies against measles after natural infection or vaccination in parturient women

Abstract

Background and aims: In Flanders, Belgium, younger women (°after 1980) have mostly been vaccinated against measles during childhood while older women have acquired natural immunity. A prospective cohort study was conducted in 2006-2007 in which women of both groups and their children are followed for 13 months to describe the kinetics and persistence of maternal antibodies against vaccine preventable diseases. The presented data show the difference in amount of antibodies in both women groups at 36 weeks of pregnancy. Vaccination status is verified in every subject with administrative documents. Methods: Immunoglobulin G (IgG) antibodies against measles were investigated by enzyme linked immunoassay (Enzygnost Dade Behring) in stored serum samples (-40°C). A regression model for log(antibody level) with linear main effects in age and status and their interaction was used for data analysis. Results: 10% of naturally infected women (N=129) had no detectable measles-IgG at childbearing age in comparison with 20% of vaccinated women (N=89), with respectively GMT (geometric mean titre) of 2911 IU/ml versus 953 IU/ml. While age did not affect the mean antibody levels significantly; a significant effect was observed between naturally infected women and vaccinated women (p= <0.001). Conclusions: Women vaccinated in their youth have significantly lower measles antibody levels at childbearing age than naturally infected women. The change of maternal measles antibodies suggest that the window of susceptibility in infants will be increasing. Follow-up data in infants will probably confirm this changing susceptibility and support decision making whether infant vaccination schedules should be adapted to serological and local epidemiological situation.